Chlamydia trachomatis is the leading bacterial cause of sexually transmitted diseases in humans worldwide. Inflammation is required for elimination of chlamydial infection, but inflammation is also responsible for pelvic inflammatory disease and scarring of upper genital tract fallopian tubes which can lead to infertility, ectopic pregnancy (a major cause of pregnancy-related death) and pelvic inflammatory disease. The maturation and secretion of inflammatory cytokines IL-1p and IL-18 are mediated by caspase-1, Which in turn, is activated following the assembly of large protein complexes named inflammasomes. The danger signal ATP is released by infected or stressed cells at sites of inflammation, and helps to control Infection through Its ability to stimulate secretion of proinflammatory cytokines. ATPe binds to the purinergic receptor P2X7 which is expressed on hemopoietic cells, fibroblasts and some epithelial cells. The binding of the P2X7 receptor and ATPe leads to the maturation and secretion of the pro-inflammatory cytokines IL-ip and IL-18 following activation of the Nalp3 inflammasome. My host laboratory has also shown that P2X7 ligation inhibits directly infection of macrophages or epithelial cells with C. trachomatis. My preliminary experiments have shown that chlamydiae produce a homolog of a nucleoside diphosphate kinase (Ndk) during infection of epithelial cells. I propose therefore that the chlamydial Ndk (cNdk) will also inhibit ATP-induced cell signaling and apoptosis of infected and uninfected macrophages and epithelial cells. Furthermore, since depletion of ATPe by cNdk should also decrease ATP-dependent inflammasome activation, I predict that cNdk should dampen secretion of inflammatory cytokines from both Chlamydia-infected cells and cells stimulated with other pathogens in the genital tract. Hypothesis: cNdk secreted from Chlamydia-infected cells will protect the host-cell from P2X7-mediated apoptosis due to the ability of cNdk to consume ATPe. Furthermore, through its ability to decrease the extracellular ATP concentration, cNdk will inhibit Nalp3 inflammasome activation in both cells infected with chlamydiae and other infected cells in the genital tract. Specific Aims: 1. Characterize the effect of chlamydial nucleoside diphosphate kinase (cNdk) on P2X7 receptor mediated cell signaling 2. Investigate the ability of cNdk to modulate the activity of the Nalp3/Cryopyrin inflammasome in cells stimulated with microbial products.